通天河干流水电梯级开发景观效应与生态安全评价

Landscape effect and ecological security evaluation of cascade hydropower development in the mainstream of Tongtian River Basin

为评价通天河干流水电开发对区域生态环境的影响,利用数字影像和野外调查等基础数据,以"3S"技术为支撑,运用景观生态学和生态安全指数等方法对通天河干流水电梯级开发引起的陆地生态环境变化进行了分析和评价。结果表明:水电梯级开发后流域内水体面积增加300.72 km^2,草地面积减少296.80 km^2,主要植被类型和土地利用格局未产生明显变化;流域景观格局中的优势景观类型为草地,其次为裸地和林地,在景观格局水平上景观破碎度降低,景观优势度增加,同时景观多样性增加,有利于区域生态系统的稳定;水电梯级开发未对流域内植被生产力和河流两岸物种丰富度造成显著影响,水电站建成后植被生产力值减小1.83×105t/a,仅占区域原植被生产力值的0.78%;水电梯级开发后流域总体生态安全指数为0.819,较开发前增大0.001,流域生态安全指数总体维持较高水平。通天河干流水电梯级开发后流域景观格局、生态系统的功能与性质未发生改变,未对流域生态环境与安全造成威胁。

In order to evaluate the impacts of hydropower development on the ecological environment, the impacts of the cascade development of hydropower projects in the main stream of the Tongtian River on the terrestrial ecological environment were analyzed and evaluated using the “3S” technology combined with the methods of landscape ecology and the ecological security index, as well as data from digital images and field surveys. The results show that, subsequent to cascade hydropower development, the water area increased by 300. 72 km2 , the grassland area decreased by 296. 80 km2 , and there was no significant change in the main vegetation types and land use patterns. Grassland was the dominant landscape type in the basin, followed by bare land and woodland. Landscape fragmentation decreased after hydropower development, while landscape dominance and diversity increased, which was conducive to the stability of regional ecosystem. Cascade hydropower development did not significantly affect the productivity of vegetation in the basin and the richness of species on both sides of the river. The productivity of vegetation decreased by 1. 83×105 t/a, and the productivity after the development only accounted for 0. 78% of that before the development. The ecological security index of the overall basin was 0. 819 after the development, 0. 001 higher than that before it, indicating a high ecological security index. In summary, since there were no major changes in landscape patterns or in ecosystem features and functions, cascade hydropower development does not pose a threat to the ecological environment and safety in the Tongtian River Basin.